Multiple output digital video recording system

ABSTRACT

A multimedia time warping system allows a user to store selected multimedia data streams while the user is simultaneously watching or reviewing other multimedia data. Data streams are converted to digital streams for internal transfer and manipulation. A parser and event buffer decouple the CPU from having to parse the digital stream. Video segments are stored on a storage device and when data is requested for display, its video segments are extracted from the storage device and sent to a decoder that converts them into display output signals and delivers the display output signals to a display.

CROSS-REFERENCE TO RELATED APPLICATIONS; BENEFIT CLAIM

This application is a continuation of U.S. Ser. No. 10/081,776, filedFeb. 20, 2002, which is a continuation of U.S. Ser. No. 09/827,029,filed Apr. 5, 2001, which is a continuation of U.S. Ser. No. 09/126,071,filed Jul. 30, 1998, now U.S. Pat. No. 6,233,389, the entire contents ofwhich are hereby incorporated by reference as if fully set forth herein.

The applicants hereby rescind any disclaimer of claim scope in theparent applications or the prosecution history thereof and advise theUSPTO that the claims in this application may be broader than any claimin the parent applications.

BACKGROUND

1. Technical Field

The invention relates to the time shifting of television broadcastsignals. More particularly, the invention relates to the real timecapture, storage, and display of television broadcast signals.

2. Description of the Prior Art

The Video Cassette Recorder (VCR) has changed the lives of television(TV) viewers throughout the world. The VCR has offered viewers theflexibility to time-shift TV programs to match their lifestyles.

The viewer stores TV programs onto magnetic tape using the VCR. The VCRgives the viewer the ability to play, rewind, fast forward and pause thestored program material. These functions enable the viewer to pause theprogram playback whenever he desires, fast forward through unwantedprogram material or commercials, and to replay favorite scenes. However,a VCR cannot both capture and play back information at the same time.

One approach to solving this problem is to use several VCRs. Forexample, if two video tape recorders are available, it might be possibleto Ping-Pong between the two. In this case, the first recorder isstarted at the beginning of the program of interest. If the viewerwishes to rewind the broadcast, the second recorder begins recording,while the first recorder is halted, rewound to the appropriate place,and playback initiated. However, at least a third video tape recorder isrequired if the viewer wishes to fast forward to some point in timeafter the initial rewind was requested. In this case, the third recorderstarts recording the broadcast stream while the second is halted andrewound to the appropriate position. Continuing this exercise, one canquickly see that the equipment becomes unwieldy, unreliable, expensive,and hard to operate, while never supporting all desired functions. Inaddition, tapes are of finite length, and may potentially end atinconvenient times, drastically lowering the value of the solution.

The use of digital computer systems to solve this problem has beensuggested. U.S. Pat. No. 5,371,551 issued to Logan et al., on 6 Dec.1994, teaches a method for concurrent video recording and playback. Itpresents a microprocessor controlled broadcast and playback device. Saiddevice compresses and stores video data onto a hard disk. However, thisapproach is difficult to implement because the processor requirementsfor keeping up with the high video rates makes the device expensive andproblematic. The microprocessor must be extremely fast to keep up withthe incoming and outgoing video data.

It would be advantageous to provide a multimedia time warping systemthat gives the user the ability to simultaneously record and play backTV broadcast programs. It would further be advantageous to provide amultimedia time warping system that utilizes an approach that decouplesthe microprocessor from the high video data rates, thereby reducing themicroprocessor and system requirements which are at a premium.

SUMMARY OF THE INVENTION

An embodiment of the invention provides a multimedia time warpingsystem. The embodiment utilizes an easily manipulated, low costmultimedia storage and display system that allows the user to view atelevision broadcast program with the option of instantly reviewingprevious scenes within the program. In addition, an embodiment allowsthe user to store selected television broadcast programs while the useris simultaneously watching or reviewing another program.

An embodiment of the invention accepts television (TV) input streams ina multitude of forms, for example, analog forms such as NationalTelevision Standards Committee (NTSC) or PAL broadcast, and digitalforms such as Digital Satellite System (DSS), Digital Broadcast Services(DBS), or Advanced Television Standards Committee (ATSC). Analog TVstreams are converted into a digital formatted stream for internaltransfer and manipulation, while pre-formatted MPEG streams areextracted from the digital TV signal and manipulated as digital streams.

The system parses the resulting digital stream and generates identifyinginformation associated with at least one video segment of the digitalstream. Events are recorded that indicate the type of segment that hasbeen found, where it is located, and when it occurred. The program logicis notified that an event has occurred and the video segment isextracted from buffers.

A parser and event buffer decouple the CPU from having to parse thedigital stream and from the real time nature of the data streams. Thisdecoupling allows for slower CPU and bus speeds which translate to lowersystem costs.

The video segments are stored on a storage device. When a program isrequested for display, its video segments are extracted from the storagedevice and reassembled into an digital stream. The digital stream issent to a decoder. The decoder converts the digital stream into displayoutput signals and delivers the display output signals to a display.

User control commands are accepted and sent through the system. Thesecommands affect the flow of the digital stream and allow the user toview stored programs with at least the following functions: reverse,fast forward, play, pause, index, fast/slow reverse play, and fast/slowplay.

Other aspects and advantages of the invention will become apparent fromthe following detailed description in combination with the accompanyingdrawings, illustrating, by way of example, the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block schematic diagram of a high level view of anembodiment of the invention according to the invention;

FIG. 2 is a block schematic diagram of an embodiment of the inventionusing multiple input and output modules according to the invention;

FIG. 3 is a schematic diagram of an Moving Pictures Experts Group (MPEG)data stream and its video and audio components according to theinvention;

FIG. 4 is a block schematic diagram of a parser and four direct memoryaccess (DMA) input engines contained in the Media Switch according tothe invention;

FIG. 5 is a schematic diagram of the components of a packetizedelementary stream (PES) buffer according to the invention;

FIG. 6 is a schematic diagram of the construction of a PES buffer fromthe parsed components in the Media Switch output circular buffers;

FIG. 7 is a block schematic diagram of the Media Switch and the variouscomponents that it communicates with according to the invention;

FIG. 8 is a block schematic diagram of a high level view of the programlogic according to the invention;

FIG. 9 is a block schematic diagram of a class hierarchy of the programlogic according to the invention;

FIG. 10 is a block schematic diagram of an embodiment of the clip cachecomponent of the invention according to the invention;

FIG. 11 is a block schematic diagram of an embodiment of the inventionthat emulates a broadcast studio video mixer according to the invention;

FIG. 12 is a block schematic diagram of a closed caption parseraccording to the invention; and

FIG. 13 is a block schematic diagram of a high level view of a preferredembodiment of the invention utilizing a VCR as an integral component ofthe invention according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the invention provides a multimedia time warpingsystem. A system according to an embodiment of the invention provides amultimedia storage and display system that allows the user to view atelevision broadcast program with the option of instantly reviewingprevious scenes within the program. The embodiment additionally providesthe user with the ability to store selected television broadcastprograms while simultaneously watching or reviewing another program andto view stored programs with at least the following functions: reverse,fast forward, play, pause, index, fast/slow reverse play, and fast/slowplay.

Referring to FIG. 1, an embodiment of the invention has an Input Section101, Media Switch 102, and an Output Section 103. The Input Section 101takes television (TV) input streams in a multitude of forms, forexample, National Television Standards Committee (NTSC) or PALbroadcast, and digital forms such as Digital Satellite System (DSS),Digital Broadcast Services (DBS), or Advanced Television StandardsCommittee (ATSC). DBS, DSS and ATSC are based on standards called MovingPictures Experts Group 2 (MPEG2) and MPEG2 Transport. MPEG2 Transport isa standard for formatting the digital data stream from the TV sourcetransmitter so that a TV receiver can disassemble the input stream tofind programs in the multiplexed signal. The Input Section 101 producesMPEG streams. An MPEG2 transport multiplex supports multiple programs inthe same broadcast channel, with multiple video and audio feeds andprivate data. The Input Section 101 tunes the channel to a particularprogram, extracts a specific MPEG program out of it, and feeds it to therest of the system. Analog TV signals are encoded into a similar MPEGformat using separate video and audio encoders, such that the remainderof the system is unaware of how the signal was obtained. Information maybe modulated into the Vertical Blanking Interval (VBI) of the analog TVsignal in a number of standard ways; for example, the North AmericanBroadcast Teletext Standard (NABTS) may be used to modulate informationonto lines 10 through 20 of an NTSC signal, while the FCC mandates theuse of line 21 for Closed Caption (CC) and Extended Data Services (EDS).Such signals are decoded by the input section and passed to the othersections as if they were delivered via an MPEG2 private data channel.

The Media Switch 102 mediates between a microprocessor CPU 106, harddisk or storage device 105, and memory 104. Input streams are convertedto an MPEG stream and sent to the Media Switch 102. The Media Switch 102buffers the MPEG stream into memory. It then performs two operations ifthe user is watching real time TV: the stream is sent to the OutputSection 103 and it is written simultaneously to the hard disk or storagedevice 105.

The Output Section 103 takes MPEG streams as input and produces ananalog TV signal according to the NTSC, PAL, or other required TVstandards. The Output Section 103 contains an MPEG decoder, On-ScreenDisplay (OSD) generator, analog TV encoder and audio logic. The OSDgenerator allows the program logic to supply images which will beoverlayed on top of the resulting analog TV signal. Additionally, theOutput Section can modulate information supplied by the program logiconto the VBI of the output signal in a number of standard formats,including NABTS, CC and EDS.

With respect to FIG. 2, the invention easily expands to accommodatemultiple Input Sections (tuners) 201, 202, 203, 204, each can be tunedto different types of input. Multiple Output Modules (decoders) 206,207, 208, 209 are added as well. Special effects such as picture in apicture can be implemented with multiple decoders. The Media Switch 205records one program while the user is watching another. This means thata stream can be extracted off the disk while another stream is beingstored onto the disk.

Referring to FIG. 3, the incoming MPEG stream 301 has interleaved video302, 305, 306 and audio 303, 304, 307 segments. These elements must beseparated and recombined to create separate video 308 and audio 309streams or buffers. This is necessary because separate decoders are usedto convert MPEG elements back into audio or video analog components.Such separate delivery requires that time sequence information begenerated so that the decoders may be properly synchronized for accurateplayback of the signal.

The Media Switch enables the program logic to associate proper timesequence information with each segment, possibly embedding it directlyinto the stream. The time sequence information for each segment iscalled a time stamp. These time stamps are monotonically increasing andstart at zero each time the system boots up. This allows the inventionto find any particular spot in any particular video segment. Forexample, if the system needs to read five seconds into an incomingcontiguous video stream that is being cached, the system simply has tostart reading forward into the stream and look for the appropriate timestamp.

A binary search can be performed on a stored file to index into astream. Each stream is stored as a sequence of fixed-size segmentsenabling fast binary searches because of the uniform time stamping. Ifthe user wants to start in the middle of the program, the systemperforms a binary search of the stored segments until it finds theappropriate spot, obtaining the desired results with a minimal amount ofinformation. If the signal were instead stored as an MPEG stream, itwould be necessary to linearly parse the stream from the beginning tofind the desired location.

With respect to FIG. 4, the Media Switch contains four input DirectMemory Access (DMA) engines 402, 403, 404, 405 each DMA engine has anassociated buffer 410, 411, 412, 413. Conceptually, each DMA engine hasa pointer 406, a limit for that pointer 407, a next pointer 408, and alimit for the next pointer 409. Each DMA engine is dedicated to aparticular type of information, for example, video 402, audio 403, andparsed events 405. The buffers 410, 411, 412, 413 are circular andcollect the specific information. The DMA engine increments the pointer406 into the associated buffer until it reaches the limit 407 and thenloads the next pointer 408 and limit 409. Setting the pointer 406 andnext pointer 408 to the same value, along with the corresponding limitvalue creates a circular buffer. The next pointer 408 can be set to adifferent address to provide vector DMA.

The input stream flows through a parser 401. The parser 401 parses thestream looking for MPEG distinguished events indicating the start ofvideo, audio or private data segments. For example, when the parser 401finds a video event, it directs the stream to the video DMA engine 402.The parser 401 buffers up data and DMAs it into the video buffer 410through the video DMA engine 402. At the same time, the parser 401directs an event to the event DMA engine 405 which generates an eventinto the event buffer 413. When the parser 401 sees an audio event, itredirects the byte stream to the audio DMA engine 403 and generates anevent into the event buffer 413. Similarly, when the parser 401 sees aprivate data event, it directs the byte stream to the private data DMAengine 404 and directs an event to the event buffer 413. The MediaSwitch notifies the program logic via an interrupt mechanism when eventsare placed in the event buffer.

Referring to FIGS. 4 and 5, the event buffer 413 is filled by the parser401 with events. Each event 501 in the event buffer has an offset 502,event type 503, and time stamp field 504. The parser 401 provides thetype and offset of each event as it is placed into the buffer. Forexample, when an audio event occurs, the event type field is set to anaudio event and the offset indicates the location in the audio buffer411. The program logic knows where the audio buffer 411 starts and addsthe offset to find the event in the stream. The address offset 502 tellsthe program logic where the next event occurred, but not where it ended.The previous event is cached so the end of the current event can befound as well as the length of the segment.

With respect to FIGS. 5 and 6, the program logic reads accumulatedevents in the event buffer 602 when it is interrupted by the MediaSwitch 601. From these events the program logic generates a sequence oflogical segments 603 which correspond to the parsed MPEG segments 615.The program logic converts the offset 502 into the actual address 610 ofeach segment, and records the event length 609 using the last cachedevent. If the stream was produced by encoding an analog signal, it willnot contain Program Time Stamp (PTS) values, which are used by thedecoders to properly present the resulting output. Thus, the programlogic uses the generated time stamp 504 to calculate a simulated PTS foreach segment and places that into the logical segment timestamp 607. Inthe case of a digital TV stream, PTS values are already encoded in thestream. The program logic extracts this information and places it in thelogical segment timestamp 607.

The program logic continues collecting logical segments 603 until itreaches the fixed buffer size. When this occurs, the program logicgenerates a new buffer, called a Packetized Elementary Stream (PES) 605buffer containing these logical segments 603 in order, plus ancillarycontrol information. Each logical segment points 604 directly to thecircular buffer, e.g., the video buffer 613, filled by the Media Switch601. This new buffer is then passed to other logic components, which mayfurther process the stream in the buffer in some way, such as presentingit for decoding or writing it to the storage media. Thus, the MPEG datais not copied from one location in memory to another by the processor.This results in a more cost effective design since lower memorybandwidth and processor bandwidth is required.

A unique feature of the MPEG stream transformation into PES buffers isthat the data associated with logical segments need not be present inthe buffer itself, as presented above. When a PES buffer is written tostorage, these logical segments are written to the storage medium in thelogical order in which they appear. This has the effect of gatheringcomponents of the stream, whether they be in the video, audio or privatedata circular buffers, into a single linear buffer of stream data on thestorage medium. The buffer is read back from the storage medium with asingle transfer from the storage media, and the logical segmentinformation is updated to correspond with the actual locations in thebuffer 606. Higher level program logic is unaware of thistransformation, since it handles only the logical segments, thus streamdata is easily managed without requiring that the data ever be copiedbetween locations in DRAM by the CPU.

A unique aspect of the Media Switch is the ability to handle high datarates effectively and inexpensively. It performs the functions of takingvideo and audio data in, sending video and audio data out, sending videoand audio data to disk, and extracting video and audio data from thedisk on a low cost platform. Generally, the Media Switch runsasynchronously and autonomously with the microprocessor CPU, using itsDMA capabilities to move large quantities of information with minimalintervention by the CPU.

Referring to FIG. 7, the input side of the Media Switch 701 is connectedto an MPEG encoder 703. There are also circuits specific to MPEG audio704 and vertical blanking interval (VBI) data 702 feeding into the MediaSwitch 701. If a digital TV signal is being processed instead, the MPEGencoder 703 is replaced with an MPEG2 Transport Demultiplexor, and theMPEG audio encoder 704 and VBI decoder 702 are deleted. Thedemultiplexor multiplexes the extracted audio, video and private datachannel streams through the video input Media Switch port.

The parser 705 parses the input data stream from the MPEG encoder 703,audio encoder 704 and VBI decoder 702, or from the transportdemultiplexor in the case of a digital TV stream. The parser 705 detectsthe beginning of all of the important events in a video or audio stream,the start of all of the frames, the start of sequence headers—all of thepieces of information that the program logic needs to know about inorder to both properly play back and perform special effects on thestream, e.g. fast forward, reverse, play, pause, fast/slow play,indexing, and fast/slow reverse play.

The parser 705 places tags 707 into the FIFO 706 when it identifiesvideo or audio segments, or is given private data. The DMA 709 controlswhen these tags are taken out. The tags 707 and the DMA addresses of thesegments are placed into the event queue 708. The frame typeinformation, whether it is a start of a video I-frame, video B-frame,video P-frame, video PES, audio PES, a sequence header, an audio frame,or private data packet, is placed into the event queue 708 along withthe offset in the related circular buffer where the piece of informationwas placed. The program logic operating in the CPU 713 examines eventsin the circular buffer after it is transferred to the DRAM 714.

The Media Switch 701 has a data bus 711 that connects to the CPU 713 andDRAM 714. An address bus 712 is also shared between the Media Switch701, CPU 713, and DRAM 714. A hard disk or storage device 710 isconnected to one of the ports of the Media Switch 701. The Media Switch701 outputs streams to an MPEG video decoder 715 and a separate audiodecoder 717. The audio decoder 717 signals contain audio cues generatedby the system in response to the user's commands on a remote control orother internal events. The decoded audio output from the MPEG decoder isdigitally mixed 718 with the separate audio signal. The resultingsignals contain video, audio, and on-screen displays and are sent to theTV 716.

The Media Switch 701 takes in 8-bit data and sends it to the disk, whileat the same time extracts another stream of data off of the disk andsends it to the MPEG decoder 715. All of the DMA engines described abovecan be working at the same time. The Media Switch 701 can be implementedin hardware using a Field Programmable Gate Array (FPGA), ASIC, ordiscrete logic.

Rather than having to parse through an immense data stream looking forthe start of where each frame would be, the program logic only has tolook at the circular event buffer in DRAM 714 and it can tell where thestart of each frame is and the frame type. This approach saves a largeamount of CPU power, keeping the real time requirements of the CPU 713small. The CPU 713 does not have to be very fast at any point in time.The Media Switch 701 gives the CPU 713 as much time as possible tocomplete tasks. The parsing mechanism 705 and event queue 708 decouplethe CPU 713 from parsing the audio, video, and buffers and the real timenature of the streams, which allows for lower costs. It also allows theuse of a bus structure in a CPU environment that operates at a muchlower clock rate with much cheaper memory than would be requiredotherwise.

The CPU 713 has the ability to queue up one DMA transfer and can set upthe next DMA transfer at its leisure. This gives the CPU 713 large timeintervals within which it can service the DMA controller 709. The CPU713 may respond to a DMA interrupt within a larger time window becauseof the large latency allowed. MPEG streams, whether extracted from anMPEG2 Transport or encoded from an analog TV signal, are typicallyencoded using a technique called Variable Bit Rate encoding (VBR). Thistechnique varies the amount of data required to represent a sequence ofimages by the amount of movement between those images. This techniquecan greatly reduce the required bandwidth for a signal, howeversequences with rapid movement (such as a basketball game) may be encodedwith much greater bandwidth requirements. For example, the HughesDirecTV satellite system encodes signals with anywhere from 1 to 10 Mb/sof required bandwidth, varying from frame to frame. It would bedifficult for any computer system to keep up with such rapidly varyingdata rates without this structure.

With respect to FIG. 8, the program logic within the CPU has threeconceptual components: sources 801, transforms 802, and sinks 803. Thesources 801 produce buffers of data. Transforms 802 process buffers ofdata and sinks 803 consume buffers of data. A transform is responsiblefor allocating and queuing the buffers of data on which it will operate.Buffers are allocated as if “empty” to sources of data, which give themback “full”. The buffers are then queued and given to sinks as “full”,and the sink will return the buffer “empty”.

A source 801 accepts data from encoders, e.g., a digital satellitereceiver. It acquires buffers for this data from the downstreamtransform, packages the data into a buffer, then pushes the buffer downthe pipeline as described above. The source object 801 does not knowanything about the rest of the system. The sink 803 consumes buffers,taking a buffer from the upstream transform, sending the data to thedecoder, and then releasing the buffer for reuse.

There are two types of transforms 802 used: spatial and temporal.Spatial transforms are transforms that perform, for example, an imageconvolution or compression/decompression on the buffered data that ispassing through. Temporal transforms are used when there is no timerelation that is expressible between buffers going in and buffers comingout of a system. Such a transform writes the buffer to a file 804 on thestorage medium. The buffer is pulled out at a later time, sent down thepipeline, and properly sequenced within the stream.

Referring to FIG. 9, a C++ class hierarchy derivation of the programlogic is shown. The TiVo Media Kernel (Tmk) 904, 908, 913 mediates withthe operating system kernel. The kernel provides operations such as:memory allocation, synchronization, and threading. The TmkCore 904, 908,913 structures memory taken from the media kernel as an object. Itprovides operators, new and delete, for constructing and deconstructingthe object. Each object (source 901, transform 902, and sink 903) ismulti-threaded by definition and can run in parallel.

The TmkPipeline class 905, 909, 914 is responsible for flow controlthrough the system. The pipelines point to the next pipeline in the flowfrom source 901 to sink 903. To pause the pipeline, for example, anevent called “pause” is sent to the first object in the pipeline. Theevent is relayed on to the next object and so on down the pipeline. Thisall happens asynchronously to the data going through the pipeline. Thus,similar to applications such as telephony, control of the flow of MPEGstreams is asynchronous and separate from the streams themselves. Thisallows for a simple logic design that is at the same time powerfulenough to support the features described previously, including pause,rewind, fast forward and others. In addition, this structure allows fastand efficient switching between stream sources, since buffered data canbe simply discarded and decoders reset using a single event, after whichdata from the new stream will pass down the pipeline. Such a capabilityis needed, for example, when switching the channel being captured by theinput section, or when switching between a live signal from the inputsection and a stored stream.

The source object 901 is a TmkSource 906 and the transform object 902 isa TmkXform 910. These are intermediate classes that define standardbehaviors for the classes in the pipeline. Conceptually, they handshakebuffers down the pipeline. The source object 901 takes data out of aphysical data source, such as the Media Switch, and places it into a PESbuffer. To obtain the buffer, the source object 901 asks the down streamobject in his pipeline for a buffer (allocEmptyBuf). The source object901 is blocked until there is sufficient memory. This means that thepipeline is self-regulating; it has automatic flow control. When thesource object 901 has filled up the buffer, it hands it back to thetransform 902 through the pushFullBuf function.

The sink 903 is flow controlled as well. It calls nextFullBuf whichtells the transform 902 that it is ready for the next filled buffer.This operation can block the sink 903 until a buffer is ready. When thesink 903 is finished with a buffer (i.e., it has consumed the data inthe buffer) it calls releaseEmptyBuf. ReleaseEmptyBuf gives the bufferback to the transform 902. The transform 902 can then hand that buffer,for example, back to the source object 901 to fill up again. In additionto the automatic flow-control benefit of this method, it also providesfor limiting the amount of memory dedicated to buffers by allowingenforcement of a fixed allocation of buffers by a transform. This is animportant feature in achieving a cost-effective limited DRAMenvironment.

The MediaSwitch class 909 calls the allocEmptyBuf method of theTmkClipCache 912 object and receives a PES buffer from it. It then goesout to the circular buffers in the Media Switch hardware and generatesPES buffers. The MediaSwitch class 909 fills the buffer up and pushes itback to the TmkClipCache 912 object.

The TmkClipCache 912 maintains a cache file 918 on a storage medium. Italso maintains two pointers into this cache: a push pointer 919 thatshows where the next buffer coming from the source 901 is inserted; anda current pointer 920 which points to the current buffer used.

The buffer that is pointed to by the current pointer is handed to theVela decoder class 916. The Vela decoder class 916 talks to the decoder921 in the hardware. The decoder 921 produces a decoded TV signal thatis subsequently encoded into an analog TV signal in NTSC, PAL or otheranalog format. When the Vela decoder class 916 is finished with thebuffer it calls releaseEmptyBuf.

The structure of the classes makes the system easy to test and debug.Each level can be tested separately to make sure it performs in theappropriate manner, and the classes may be gradually aggregated toachieve the desired functionality while retaining the ability toeffectively test each object.

The control object 917 accepts commands from the user and sends eventsinto the pipeline to control what the pipeline is doing. For example, ifthe user has a remote control and is watching TV, the user presses pauseand the control object 917 sends an event to the sink 903, that tells itpause. The sink 903 stops asking for new buffers. The current pointer920 stays where it is at. The sink 903 starts taking buffers out againwhen it receives another event that tells it to play. The system is inperfect synchronization; it starts from the frame that it stopped at.

The remote control may also have a fast forward key. When the fastforward key is pressed, the control object 917 sends an event to thetransform 902 that tells it to move forward two seconds. The transform902 finds that the two second time span requires it to move forwardthree buffers. It then issues a reset event to the downstream pipeline,so that any queued data or state that may be present in the hardwaredecoders is flushed. This is a critical step, since the structure ofMPEG streams requires maintenance of state across multiple frames ofdata, and that state will be rendered invalid by repositioning thepointer. It then moves the current pointer 920 forward three buffers.The next time the sink 903 calls nextFullBuf it gets the new currentbuffer. The same method works for fast reverse in that the transform 902moves the current pointer 920 backwards.

A system clock reference resides in the decoder. The system clockreference is sped up for fast play or slowed down for slow play. Thesink simply asks for full buffers faster or slower, depending on theclock speed.

With respect to FIG. 10, two other objects derived from the TmkXformclass are placed in the pipeline for disk access. One is calledTmkClipReader 1003 and the other is called TmkClipWriter 1001. Bufferscome into the TmkClipWriter 1001 and are pushed to a file on a storagemedium 1004. TmkClipReader 1003 asks for buffers which are taken off ofa file on a storage medium 1005. A TmkClipReader 1003 provides only theallocEmptyBuf and pushFullBuf methods, while a TmkClipWriter 1001provides only the nextFullBuf and releaseEmptyBuf methods. ATmkClipReader 1003 therefore performs the same function as the input, or“push” side of a TmkClipCache 1002, while a TmkClipWriter 1001 thereforeperforms the same function as the output, or “pull” side of aTmkClipCache 1002.

Referring to FIG. 11, an embodiment that accomplishes multiple functionsis shown. A source 1101 has a TV signal input. The source sends data toa PushSwitch 1102 which is a transform derived from TmkXform. ThePushSwitch 1102 has multiple outputs that can be switched by the controlobject 1114. This means that one part of the pipeline can be stopped andanother can be started at the user's whim. The user can switch todifferent storage devices. The PushSwitch 1102 could output to aTmkClipWriter 1106, which goes onto a storage device 1107 or write tothe cache transform 1103.

An important feature of this apparatus is the ease with which it canselectively capture portions of an incoming signal under the control ofprogram logic. Based on information such as the current time, or perhapsa specific time span, or perhaps via a remote control button press bythe viewer, a TmkClipWriter 1106 may be switched on to record a portionof the signal, and switched off at some later time. This switching istypically caused by sending a “switch” event to the PushSwitch 1102object.

An additional method for triggering selective capture is throughinformation modulated into the VBI or placed into an MPEG private datachannel. Data decoded from the VBI or private data channel is passed tothe program logic. The program logic examines this data to determine ifthe data indicates that capture of the TV signal into which it wasmodulated should begin. Similarly, this information may also indicatewhen recording should end, or another data item may be modulated intothe signal indicating when the capture should end. The starting andending indicators may be explicitly modulated into the signal or otherinformation that is placed into the signal in a standard fashion may beused to encode this information.

With respect to FIG. 12, an example is shown which demonstrates how theprogram logic scans the words contained within the closed caption (CC)fields to determine starting and ending times, using particular words orphrases to trigger the capture. A stream of NTSC or PAL fields 1201 ispresented. CC bytes are extracted from each odd field 1202, and enteredin a circular buffer 1203 for processing by the Word Parser 1204. TheWord Parser 1204 collects characters until it encounters a wordboundary, usually a space, period or other delineating character. Recallfrom above, that the MPEG audio and video segments are collected into aseries of fixed-size PES buffers. A special segment is added to each PESbuffer to hold the words extracted from the CC field 1205. Thus, the CCinformation is preserved in time synchronization with the audio andvideo, and can be correctly presented to the viewer when the stream isdisplayed. This also allows the stored stream to be processed for CCinformation at the leisure of the program logic, which spreads out load,reducing cost and improving efficiency. In such a case, the words storedin the special segment are simply passed to the state table logic 1206.

During stream capture, each word is looked up in a table 1206 whichindicates the action to take on recognizing that word. This action maysimply change the state of the recognizer state machine 1207, or maycause the state machine 1207 to issue an action request, such as “startcapture”, “stop capture”, “phrase seen”, or other similar requests.Indeed, a recognized word or phrase may cause the pipeline to beswitched; for example, to overlay a different audio track if undesirablelanguage is used in the program.

Note that the parsing state table 1206 and recognizer state machine 1207may be modified or changed at any time. For example, a different tableand state machine may be provided for each input channel. Alternatively,these elements may be switched depending on the time of day, or becauseof other events.

Referring to FIG. 11, a PullSwitch is added 1104 which outputs to thesink 1105. The sink 1105 calls nextFullBuf and releaseEmptyBuf to get orreturn buffers from the PullSwitch 1104. The PullSwitch 1104 can haveany number of inputs. One input could be an ActionClip 1113. The remotecontrol can switch between input sources. The control object 1114 sendsan event to the PullSwitch 1104, telling it to switch. It will switchfrom the current input source to whatever input source the controlobject selects.

An ActionClip class provides for sequencing a number of different storedsignals in a predictable and controllable manner, possibly with theadded control of viewer selection via a remote control. Thus, it appearsas a derivative of a TmkXform object that accepts a “switch” event forswitching to the next stored signal.

This allows the program logic or user to create custom sequences ofvideo output. Any number of video segments can be lined up and combinedas if the program logic or user were using a broadcast studio videomixer. TmkClipReaders 1108, 1109, 1110 are allocated and each is hookedinto the PullSwitch 1104. The PullSwitch 1104 switches between theTmkClipReaders 1108, 1109, 1110 to combine video and audio clips. Flowcontrol is automatic because of the way the pipeline is constructed. ThePush and Pull Switches are the same as video switches in a broadcaststudio.

The derived class and resulting objects described here may be combinedin an arbitrary way to create a number of different usefulconfigurations for storing, retrieving, switching and viewing of TVstreams. For example, if multiple input and output sections areavailable, one input is viewed while another is stored, and apicture-in-picture window generated by the second output is used topreview previously stored streams. Such configurations represent aunique and novel application of software transformations to achieve thefunctionality expected of expensive, sophisticated hardware solutionswithin a single cost-effective device.

With respect to FIG. 13, a high-level system view is shown whichimplements a VCR backup. The Output Module 1303 sends TV signals to theVCR 1307. This allows the user to record TV programs directly on tovideo tape. The invention allows the user to queue up programs from diskto be recorded on to video tape and to schedule the time that theprograms are sent to the VCR 1307. Title pages (EPG data) can be sent tothe VCR 1307 before a program is sent. Longer programs can be scaled tofit onto smaller video tapes by speeding up the play speed or droppingframes.

The VCR 1307 output can also be routed back into the Input Module 1301.In this configuration the VCR acts as a backup system for the MediaSwitch 1302. Any overflow storage or lower priority programming is sentto the VCR 1307 for later retrieval.

The Input Module 1301 can decode and pass to the remainder of the systeminformation encoded on the Vertical Blanking Interval (VBI). The OutputModule 1303 can encode into the output VBI data provided by theremainder of the system. The program logic may arrange to encodeidentifying information of various kinds into the output signal, whichwill be recorded onto tape using the VCR 1307. Playing this tape backinto the input allows the program logic to read back this identifyinginformation, such that the TV signal recorded on the tape is properlyhandled. For example, a particular program may be recorded to tape alongwith information about when it was recorded, the source network, etc.When this program is played back into the Input Module, this informationcan be used to control storage of the signal, presentation to theviewer, etc.

One skilled in the art will readily appreciate that such a mechanism maybe used to introduce various data items to the program logic which arenot properly conceived of as television signals. For instance, softwareupdates or other data may be passed to the system. The program logicreceiving this data from the television stream may impose controls onhow the data is handled, such as requiring certain authenticationsequences and/or decrypting the embedded information according to somepreviously acquired key. Such a method works for normal broadcastsignals as well, leading to an efficient means of providing non-TVcontrol information and data to the program logic.

Additionally, one skilled in the art will readily appreciate thatalthough a VCR is specifically mentioned above any multimedia recordingdevice (e.g., a Digital Video Disk-Random Access Memory (DVD-RAM)recorder) is easily substituted in its place.

Although the invention is described herein with reference to thepreferred embodiment, one skilled in the art will readily appreciatethat other applications may be substituted for those set forth hereinwithout departing from the spirit and scope of the present invention.For example, the invention can be used in the detection of gamblingcasino crime. The input section of the invention is connected to thecasino's video surveillance system. Recorded video is cached andsimultaneously output to external VCRs. The user can switch to any videofeed and examine (i.e., rewind, play, slow play, fast forward, etc.) aspecific segment of the recorded video while the external VCRs are beingloaded with the real-time input video. Accordingly, the invention shouldonly be limited by the Claims included below.

1. A method for a digital video recorder, comprising the steps of:storing a plurality of multimedia programs in digital form on at leastone storage device; wherein a user selects previously recordedmultimedia program(s) from the at least one storage device;simultaneously retrieving for play back a video segment from at leastone of the selected previously recorded multimedia program(s) and avideo segment from a multimedia program whose storage is in progressusing video segment identifying information generated by the digitalvideo recorder for at least one video segment in the at least one of theselected previously recorded multimedia program(s) and video segmentidentifying information generated by the digital video recorder for atleast one video segment in the multimedia program whose storage is inprogress to cause delivery of selected video segments to an outputsubsystem, the digital video recorder automatically generating videosegment identifying information for specific video segments inmultimedia programs; and wherein the simultaneously retrieving for playback step allows playback rate and direction of each multimedia programto be controlled individually and simultaneously to perform any of: fastforward, rewind, frame step, pause, and play functions.
 2. The method ofclaim 1, wherein the output subsystem converts the at least one of theselected multimedia program(s) and the multimedia program whose storageis in progress into display output signals.
 3. The method of claim 2,further comprising the step of: inserting on-screen displays into adisplay output signal.
 4. The method of claim 1, wherein a user controlsplayback rate and direction of a multimedia program through a remotecontrol.
 5. The method of claim 1, wherein the retrieving for play backstep sends a multimedia program to a multimedia recording device,allowing a user to record the multimedia program.
 6. The method of claim1, further comprising the step of: creating custom sequences of videoand/or audio output; and wherein the creating step allows any number ofvideo and/or audio segments of multimedia programs to be lined up andcombined and stored on the at least one storage device.
 7. The method ofclaim 1, further comprising the step of: accepting analog and/or digitalmultimedia program signals using a plurality of input signal tuners; andwherein each of the tuners is individually tuned to a specificmultimedia program.
 8. The method of claim 7, further comprising thestep of: synchronizing video and audio components for proper playback.9. The method of claim 7, wherein an input signal tuner receives any of:software updates or data.
 10. The method of claim 1, wherein the playingback step plays back the at least one of the selected multimediaprogram(s) and the multimedia program whose storage is in progress in apicture in a picture format to a display device.
 11. An apparatus for adigital video recorder, comprising: a subsystem for storing a pluralityof multimedia programs in digital form on at least one storage device;wherein a user selects previously recorded multimedia program(s) fromthe at least one storage device; a subsystem for simultaneouslyretrieving for play back a video segment from at least one of theselected previously recorded multimedia program(s) and a video segmentfrom a multimedia program whose storage is in progress using videosegment identifying information generated by the digital video recorderfor at least one video segment in the at least one of the selectedpreviously recorded multimedia program(s) and video segment identifyinginformation generated by the digital video recorder for at least onevideo segment in the multimedia program whose storage is in progress tocause delivery of selected video segments to an output subsystem, thedigital video recorder automatically generating video segmentidentifying information for specific video segments in multimediaprograms; and wherein the simultaneously retrieving for play backsubsystem allows playback rate and direction of each multimedia programto be controlled individually and simultaneously to perform any of: fastforward, rewind, frame step, pause, and play functions.
 12. Theapparatus of claim 11, wherein the output subsystem converts the atleast one of the selected multimedia program(s) and the multimediaprogram whose storage is in progress into display output signals. 13.The apparatus of claim 12, further comprising: a subsystem for insertingon-screen displays into a display output signal.
 14. The apparatus ofclaim 11, wherein a user controls playback rate and direction of amultimedia program through a remote control.
 15. The apparatus of claim11, further comprising: a multimedia recording device, wherein theretrieving for play back subsystem sends a multimedia program to themultimedia recording device, allowing a user to record the multimediaprogram.
 16. The apparatus of claim 11, further comprising: a subsystemfor creating custom sequences of video and/or audio output; and whereinthe creating subsystem allows any number of video and/or audio segmentsof multimedia programs to be lined up and combined and stored on the atleast one storage device.
 17. The apparatus of claim 11, furthercomprising: a plurality of input signal tuners; wherein the tunersaccept analog and/or digital multimedia program signals; and whereineach of the tuners is individually tuned to a specific multimediaprogram.
 18. The apparatus of claim 17, further comprising: a subsystemfor synchronizing video and audio components for proper playback. 19.The apparatus of claim 17, wherein an input signal tuner receives anyof: software updates or data.
 20. The apparatus of claim 11, wherein theplaying back subsystem plays back the at least one of the selectedmultimedia program(s) and the multimedia program whose storage is inprogress in a picture in a picture format to a display device.
 21. Acomputer-readable medium carrying one or more sequences of instructionsfor a digital video recorder, which instructions, when executed by oneor more processors, cause the one or more processors to perform a methodcomprising: storing a plurality of multimedia programs in digital formon at least one storage device; wherein a user selects previouslyrecorded multimedia program(s) from the at least one storage device;simultaneously retrieving for play back a video segment from at leastone of the selected previously recorded multimedia program(s) and avideo segment from a multimedia program whose storage is in progressusing video segment identifying information generated by the digitalvideo recorder for at least one video segment in the at least one of theselected previously recorded multimedia program(s) and video segmentidentifying information generated by the digital video recorder for atleast one video segment in the multimedia program whose storage is inprogress to cause delivery of selected video segments to an outputsubsystem, the digital video recorder automatically generating videosegment identifying information for specific video segments inmultimedia programs; and wherein the simultaneously retrieving for playback step allows playback rate and direction of each multimedia programto be controlled individually and simultaneously to perform any of: fastforward, rewind, frame step, pause, and play functions.
 22. Thecomputer-readable medium of claim 21, wherein the output subsystemconverts the at least one of the selected multimedia program(s) and themultimedia program whose storage is in progress into display outputsignals.
 23. The computer-readable medium of claim 22, furthercomprising: inserting on-screen displays into a display output signal.24. The computer-readable medium of claim 21, wherein a user controlsplayback rate and direction of a multimedia program through a remotecontrol.
 25. The computer-readable medium of claim 21, wherein theretrieving for play back step sends a multimedia program to a multimediarecording device, allowing a user to record the multimedia program. 26.The computer-readable medium of claim 21, further comprising: creatingcustom sequences of video and/or audio output; and wherein the creatingstep allows any number of video and/or audio segments of multimediaprograms to be lined up and combined and stored on the at least onestorage device.
 27. The computer-readable medium of claim 21, furthercomprising: accepting analog and/or digital multimedia program signalsusing a plurality of input signal tuners; and wherein each of the tunersis individually tuned to a specific multimedia program.
 28. Thecomputer-readable medium of claim 27, further comprising: synchronizingvideo and audio components for proper playback.
 29. Thecomputer-readable medium of claim 27, wherein an input signal tunerreceives any of: software updates or data.
 30. The computer-readablemedium of claim 21, wherein the playing back step plays back the atleast one of the selected multimedia program(s) and the multimediaprogram whose storage is in progress in a picture in a picture format toa display device.